Ideal Case Studies Using Coupled HWRF-HYCOM

We investigate the role of ocean in tropical cyclone forecasts using the coupled Hurricane Weather Research Forecast (HWRF)-Hybrid Coordinate Ocean Model (HYCOM) system. Experiments were designed for ideal cases with a vortex on a beta-plane, both uncoupled and coupled to a 1D and a 3D ocean model. Numerical solutions for the atmospheric model component are sought, using a triple-nested domain at a resolution of 18/6/2 km on rotated latitude-longitude earth coordinates and 60 pressure-sigma hybrid levels, and those for the ocean model at 1/12^o horizontal resolution grids and 20 vertical hybrid levels. The subscale mixing is simulated using the K-Profile Parameterization (KPP) for both 1D and 3D ocean simulations. Uncoupled model predicts the strongest intensity, as opposed to the 3D coupled run which. While the uncoupled TC is predicted to be deep and compact at a radius of 30 km persistent over a 5-day forecast period, relatively large and shallow storm predicted with the 3D coupled run may be associated with variations in the upper level caused by air-sea flux interactions. We plan further investigations and detailed results will be presented for all idealized experiments.